Method for preparing the same



United States Patent 3,125,520 OIL DISPERSEONS 0F METALLIC SULFIDES AND METHOD FOR PREPARING THE SAlVIE Herbert Myers, Merchantville, N.J., assignor to Socony Mobil Oil Company, Inc, a corporation of New York No Drawing. Filed Mar. 31, 1961, Ser. No. 99,672 7 Claims. (Cl. 25225) This invention relates to colloidal dispersions of oilinsoluble metal sulfides in lubricating oil and to a novel method for preparing such dispersions.

Various oil-insoluble metallic sulfides have been known for some time to be effective as additives, particularly as anti-oxidants and extreme pressure agents, for greases. The oil-insolubility of these metal sulfides has not been a ,problem insofar as their use in greases is concerned due to the solid or semi-solid nature of grease compositions. Thus by virtue of the thickening agents utilized in greases (fatty acid soap, silica gel, etc.) the metal sulfides are held in substantial stable admixture therein. To date, however, the use of these oil-insoluble metal sulfides as additives for liquid lubricating oil compositions has not been feasible due to the problem of maintaining effective improving amounts thereof in stable distribution in the oil. Manifestly, the provision of some means whereby stable homogeneous liquid lubricating oil compositions containing the metal sulfides can be prepared would be a valuble contribution to the lubricating art. Such a means is provided by the present invention in accordance with which the oil-insoluble metal sulfides are incorporated in lubricating oils in the form of colloidal dispersions. As far as is known such lubricating oil dispersions of oil-insoluble metal sulfides have not been known heretofore and they are, therefore, considered to be new compositions of matter. Accordingly, it is the primary object of the present invention to provide a novel method for forming colloidal dispersions of oil-insoluble metal sulfides in lubricating oil. It is a further object to provide new compositions of matter comprising such colloidal dispersions. Other and further objects of the invention will become apparent from the following detailed description thereof.

Broadly stated, the method of the present invention comprises the following steps: (1) forming an aqueous colloidal metal sulfide dispersion, said dispersion (sol) containing at protecting colloid, (2) forming a mixture of said dispersion with (a) a water-soluble alcohol and (b) a lubricating oil solution of a normal polyvalent metal salt of an organic acid, whereby the colloidal metal sulfide is extracted from the aqueous metal sulfide sol and redispersed in the lubricating oil, and (3) removing the water and alcohol from said mixture to isolate a colloidal dispersion of the metal sulfide in lubricating oil.

I The manner of preparation of an aqueous metal sulfide sol utilizable as the starting material in the process of the invention is well known to the art. Typical procedures for preparing such sols of zinc sulfide and cadmium sulfide are given in Examples 1 and 7 hereinbelow.

As is also well known, protecting colloids are 13/0- philic colloids which stabilize aqueous colloidal dispersions. Examples of such colloids are gelatin, tannin, gum arabic, casein, glue, starch, albumen, etc. Although gelatin was utilized as the protecting colloid in Examples 1 and 7, any colloid of this character can be used. As shown in the examples, 1 or 2% of the gelatin was employed to prevent the colloidal metal sulfide from being precipitated upon addition of the alcohol. It has been found that these amounts are generally satisfactory although the use of greater amounts, say up to will do no harm. Also, in certain instances, such as where the concentration of the metal sulfide in the sol is relatively small, as little as 0.1% will be suflicient.

As afore-indicated the alcohols utilizable in the invention are the water-soluble aliphatic alcohols, such as methanol, ethanol, isopropanol, ethylene glycol and the like. It has been found that the alcohol must be added to the aqueous metal sulfide sol in a proportion of at least about one-fourth part thereof per part of sol in order to effect the subsequent transfer of the colloidal metal sulfide from the aqueous phase to the lubricating oil phase, the amount usually employed being from about one-half part to about two parts per part of sol. Although larger amounts of alcohol can be utilized in most instances without causing precipitation of the metal sulfide from the aqueous sol, no particular advantage is provided thereby while the time required for the removal of the alcohol after the extraction step is unnecessarily increased.

Obviously, the oil-insoluble metal sulfides to which the invention is applicable must also be water-insoluble since an aqueous sol of the metal sulfide is required as starting material in the process of the invention. The principle of the invention, however, is applicable to all waterinsoluble metal sulfides of which the sulfides of silver, copper, zinc, cadmium, bismuth, antimony, arsenic, molybdenum, nickel and cobalt may be mentioned as nonlimiting examples.

The oil-soluble organic acid salts suitable as the eX- tractant-dispersant agent in step 2 of the process of the invention are restricted to the normal salts of the metals of Group II of Mendeleffs Periodic Table of the Elements. Thus, attempts to prepare the oil dispersions of the metal sulfides by the method of the invention utilizing a basic metal salt, such as basic barium sulfonate, or a monovalent metal salt, such as potassium sulfonate, were unsuccessful, the metal sulfide being precipitated in each instance instead of being extracted and dispersed in the lubricating oil. The amount of oil-soluble salt present in the oil solution thereof should be sufficient to supply from about 0.1 to about 1.0 equivalent of metal per equivalent of metal present in the aqueous metal sulfide sol.

The oil-soluble salts utilizable as extractant-dispersant agents in the process of the invention may be derived from various oil-soluble organic acids. Thus, metal sulfonates, naphthenates, carboxylates, phosphates, thiophosphates, etc. may be used. The metal sulfonates, however, are particularly preferred. The sulfonic acids from which the latter salts may be prepared are those having molecular weights of from about 300 to about 800. These acids may be produced by the sulfonation of petroleum stocks or synthetic alkyl aromatic compounds, such as alkylsubstituted benzenes or naphthalenes, wherein the alkyl groups attached to the aromatic ring contain from at least about 8 to about 24 or more carbon atoms. Suitable synthetic sulfonic acids are, for example, octyl-benzene sulfonic acid, dodecyl-benzene sulfonic acid, dioctyl-benzene sulfonic acid, octadecyl-benzene sulfonic acid, waxbenzene sulfonic acid and wax-naphthalene sulfonic acid. Of the various acids, the wax-benzene and wax-naphthalene sulfonic acids and mixed alkyl aromatic sulfonic acids (sulfonic acid-A below) are preferred. The petroleum sulfonic acids are those obtained in the treatment of petroleum oils, particularly refined or semi-refined oils, with concentrated or fuming sulfuric acid and which remain in the oil after settling out of sludge. A typical sulfonic acid (sulfonic acid-A) which Was utilized in the examples presented hereinafter was prepared as follows.

Preparation of Sulfonic Acid-A A wax-benzene (2l2) was prepared as follows: A paraffin wax having an average of 24 carbon atoms per molecule and a melting point of 126 F. was chlorinated at a temperature of about 100 C. with chlorine gas until the weight of the wax had increased about 12%. The chlorowax thus obtained was then blown with nitrogen to remove any occluded chlorine and hydrogen chloride.

A 1000-gram portion of the chlorowax was then mixed with 500 grams of benzene in a 3-necked flask equipped with a stirrer, reflux condenser and a thermometer. The mixture was heated to a temperature of 60 C. Aluminum chloride was then added slowly over a period of two hours. The addition of aluminum chloride was accompanied by a vigorous evolution of hydrogen chloride. The temperature was then raised to a temperature of 80 C. and held there for one hour. The excess benzene was then removed by inverting the reflux condenser and heating to a temperature of 116 C. Two hundred milliliters of benzene were thus recovered. The mixture was cooled to a temperature of 60 C. and then another 1000 grams of chlorowax were added. After completing the addition of this chlorowax, the temperature was raised to 100 C. and held there for one hour. The product was allowed to stand overnight at a temperature of about 60 C., and then was separated from the sludge by decantation and filtered by suction through clay.

It will be understood that a wax-benzene prepared according to the foregoing procedure in which a quantity of chlorowax containing 2 atomic proportions of chlorine and having a chlorine content of 12% is reacted with 1 mol of benzene is designated wax-benzene (212). Similarly, wax-benzene (310) and wax-benzene (1-10) may also be prepared by the reaction of sufficient amounts of chlorinated wax, containing 10%, by weight, of chloride, to provide 3 atomic proportions and 1 atomic proportion of chlorine per mol of benzene, respectively, in the reaction and are useful in the invention. In general, the amount of chlorowax containing from about 10% to about 18%, by weight, of chlorine used in the reaction is sufficient to supply between 1 and 4 atomic proportions of chlorine per mol of benzene used.

A sulfonic acid was prepared by sulfonating a mixture composed of 63 mol percent of wax-benzene (2-12), prepared as above, and 37 mol percent of a high-boiling hydrocarbon fraction obtained as a by-product in the manufacture of dodecyl benzene. This fraction is cmposed predominantly of alkyl aromatics (60-80 weight percent), the remainder being non-aromatics. The particular fraction used has a boiling range of 592-828 R, an API gravity of 292 and a flash point of 370 F. The sulfonation was conducted as follows. 1738 grams of the wax-benzene-by-product fraction mixture were placed in a B-necked flask equipped with a stirrer and a thermometer and heated to a temperature of 40 C. 869 grams of oleum (15% 80,) were added slowly from a dropping funnel at a rate regulated to maintain the temperature below 50 C. The addition of oleum consumed about 3 hours. The mixture was then stirred for an additional hour to insure complete reaction. The mixture was then poured into 1000 milliliters of water and subsequently 1810 grams of mineral oil were added. The mixture thus obtained was stirred thoroughly and then allowed to stand until the water separated into a layer. The water layer was then drained off. The mixed waxbenzene (2-12)-alkyl aromatic sulfonic acid thus produced had a total N, N of 68 and a true N, N of 63.

Several polyvalent metal salts of sulfonic acid-A were prepared by conventional procedures and were utilized as the extractant-dispersant agents in the illustrative examples presented hereinafter.

As shown in the examples, the removal of the alcoholic aqueous phase in step 3 of the process of the invention may be effected by either of two procedures, viz., (1) the mixture from step 2 is separated by stratification into an aqueous alcohol phase and a lubricating oil phase, after which residual water and alcohol are distilled from the lubricating oil phase or (2) the mixture may be subjected to distillation directly, i.e., without Stratification, to remove the water and alcohol. A preferred procedure is to add a non-polar solvent, such as benzene, toluene, etc., to the mixture of step 2 along with the mineral oil solution of the dispersant metal salt, whereby, after separation of the two phases, the residual water and alcohol are distilled from the non-polar (solvent-lubricating oil) phase as an azeotrope with the solvent. After the water and alcohol are distilled off, the distillation is continued in order to remove the solvent.

A full understanding of the invention may be had by reference to the following illustrative examples. In these examples percent excess zinc and percent excess cadmium represent the percentage of either zinc or cadmium present in the product oil dispersion over and above the metal content thereof due to the metal of the normal metal sulfonate utilized as the extractant-dispersant agent.

Example 1 A solution of 36.5 grams (0.4 equivalent) of zinc sulfate monohydrate in 275 milliliters of water was treated with milliliters of concentrated ammonium hydroxide, chilled to 15 C. and saturated with hydrogen sulfide. The resulting White zinc sulfide precipitate was filtered off, washed with water and redisbursed in 750 milliliters of water containing 1% gelatin. This dispersion was again saturated with hydrogen sulfide at 15 C., stoppered and allowed to stir overnight. During this period, the zinc sulfide completely peptized forming a pale yellow sol containing approximately 0.05 equivalent of zinc per 100 milliliters of sol.

Example 2 A mixture of 200 milliliters (0.1 equivalent of zinc) of the aqueous zinc sulfide sol prepared in Example 1, 300 milliliters of methanol, 40 grams (0.02 equivalent) of a normal zinc salt of sulfonic acid-A (1.7% zinc), 40 grams of a parafiinic mineral oil having a viscosity of 100 SUS at 100 F. and 300 milliliters of benzene was charged to a separatory funnel and vigorously shaken. The phases were separated and the benzene solution azeotroped over a Dean-Stark takeoff to remove the residual water and methanol. The benzene was then removed by topping to a pot temperature of C. with vigorous nitrogen blowing and the residue filtered through diatomaceous earth to give a fluid, slightly opalescent sol which analyzed 4.9% zinc (percent excess zinc=5l0).

Example 3 A mixture of 400 milliliters (0.2 equivalent of zinc) of the aqueous zinc sulfide sol prepared in Example 1, 240 milliliters of methanol, 38 grams (0.02 equivalent) of a normal zinc salt of sulfonic acid-A (1.7% zinc), 35 grams of a parafiinic mineral oil having a viscosity of 100 SUS at 100 F. and 100 milliliters of benzene was charged to a one-liter flask equipped with a Dean-Stark takeoff, condenser, stirrer and thermometer. The reaction mixture was then heated to 95 C. with the volatile materials being removed through the Dean-Stark takeoff. At this point, 200 milliliters of toluene Was added and the remainder of the water removed azeotropically. The toluene was then stripped off to a pot temperature of C. at 2 millimeters of pressure and the residue filtered through diatomaceous earth to give a fluid, opalescent product sol containing 7.7% zinc (percent excess zinc=900).

Example 4 A mixture of 200 milliliters (0.1 equivalent of zinc) of the aqueous zinc sulfide sol prepared in Example 1, 300 milliliters of methanol, 93 grams (0.07 equivalent) of a normal calcium salt of sulfonic acid-A (1.5% calcium), 7 grams of a paraflinic mineral oil having a viscosity of 100 SUS at 100 F. and 100 milliliters of benzene was charged to a separatory funnel and vigorously shaken.

The phases were separated and the benzene solution azeotroped over a Dean-Stark ta'keofi to remove the residual water and methanol. The benzene was then removed by topping to a pot temperature of 140 C. with nitrogen blowing and the residue filtered through diatomaceous earth to give a viscous, slightly opalescent sol product, which analyzed 2.0% zinc and 1.0% calcium (percent excess zinc: 160) Example 5 A mixture of 200 milliliters (0.1 equivalent of zinc) of the aqueous zinc sulfide sol prepared in Example 1, 300 milliliters of methanol, 145 grams (0:1 equivalent) of a normal magnesium salt of sulfonic acid-A (0.86% magnesium) and 150 milliliters of benzene was charged to a separatory tunnel and shaken vigorously. The phases were separated and the benzene solution azeotroped over Dean-Stark takeofi to remove the residual water and )methanol. The benzene was then removed by topping to a pot temperature of 130 C. with vigorous nitrogen blowing and the residue filtered through diatomaceous earth to give a viscous, bright sol product analyzing 1.2% zinc and 0.5% magnesium (percent excess zinc=90).

Example 6 A mixture or 225 milliliters (0.1 equivalent of zinc) of the aqueous zinc sulfide sol prepared in Example 1, 135 milliliters of methanol, 150 grams (0.1 equivalent) of a normal lead salt of sulfoni-c acid-A (6.8% lead) and 150 milliliters of benzene was charged to a one-liter flask equipped with a Dean-Stark takeoff, condenser, stirrer and thermometer. The reaction mixture was then heated to 100 C. with the volatile materials being removed through the DeamSt-ark takeoff. At this point, 200 milliliters of benzene was added and the remainder of the water removed azeotropically. The benzene was then stripped off to a pot temperature of 125 C. with vigorous nitrogen blowing and the residue filtered through diatornaceous earth to give a dark, fluid sol product analyzing 1.9% zinc and 6.9% lead (percent excess zinc=100).

Example 7 -An aqueous cadmium sulfide sol was prepared as .follows. A solution of 57.0 grams (0.43 equivalent) of cadmium acetate dihydrate in 500 milliliters of water was treated with 200 milliliters of concentrated ammonium hydroxide and saturated with hydrogen sulfide at C. The resulting yellow cadmium sulfide was isolated, washed twice with water and redisbursed in 2 liters of water containing 2.0% gelatin. dispersion was again saturated with hydrogen sulfide at 15 C., stoppered and stirred overnight. During this period, the cadmium sul fide completely peptized forming a deep yellow sol containing approximately 0.2 equivalent of cadmium sulfide per liter of sol.

Example 8 A mixture of 875 milliliters (0.175 equivalent of cadmium sulfide) of the above aqueous cadmium sulfide sol prepared in Example 7 and 525 milliliters of methanol was vigorously shaken in a separatory tunnel with a solution of 90 grams (0.04 equivalent)= of a normal cadmium salt of sulfonic acid-A (2.4% cadmium) 50 grams of diluent mineral lubricating oil and 200 milliliters of benzene. The resulting viscous emulsion was topped to 100 C.; treated with 200 milliliters of toluene and the remaining water azeot-ropically removed. An additional 260 grams of diluent mineral oil was then added and the toluene removed by heating to 150 C. with vigorous nitrogen blowing. The resulting residue was filtered through diatomaceous earth to give :a viscous, yellow opalescent sol which analyzed 5.8% cadmium (percent excess cadmium: 270).

As shown in the foregoing examples, the colloidal dispersions provided by the invention contain substantial concentrations of metal sulfide which are equal to or over and above that ordinarily required for improving lubricating oil compositions in various respects. Thus, it will be seen, for example, that the dispersion prepared in Example 4, having a total zinc content of 7.7% and containing 900% excess Zinc (i.e., zinc as zinc sulfide) contains 10.3% of dispersed Zinc sulfide. Accordingly, these dispersions may be used either per so as lubricating oils or they may be blended with lubricating oil base stocks in amounts required to improve the extreme pressure, antioxidant and detergent characteristics of finished oils.

The oil dispersions provided by the invention may be used in lubricating oil compositions containing other additives designed to improve the various characteristics of the oil, such as pour point depressants, viscosity index improvers, etc. They may also be used in oils in combination with other extreme pressure agents, detergents and antioxidants.

Although the present invention has been described herein by means of certain specific embodiments and illustrat-ive examples, it is not intended that the scope thereof be limited in any way thereby, but only as indicated in the following claims.

What is claimed is: g

1. A method for preparing a colloidal dispersion of metal sulfide in lubricating oil which comprises the steps of (1) forming an aqueous metal sulfide sol, said sol containing from about 0.1% to about 5% of a protecting colloid, (2) forming a mixture of said sol with (a) a Water-soluble aliphatic alcohol in an amount to supply to said mixture at least about one-fourth part of alcohol per part of said sol and (b) a lubricating oil solution of a normal metal salt of an oil-soluble sulfonic acid having a molecular weight of from about 300 to about 800, the metal constituent of which is a metal of Group II of Mendeleffs Periodic Table of the Elements, in an amount to supply to said mixture from about 0.1 to about 1.0 equivalent of metal per equivalent of metal supplied by said sol, whereby the colloidal metal sulfide is extracted from said sol and redispersed in the lubricating oil, and (3) removing the water and alcohol from said mixture to isolate the colloidal dispersion of metal sulfide in lubricating oil.

2. A method for preparing a colloidal dispersion of Zinc sulfide in lubricating oil which comprises the steps of (1) forming an aqueous zinc sulfide sol, said sol containing from about 0.1% to about 5% of at protecting colloid, (2) forming a mixture of said sol with (a) a water-soluble aliphatic alcohol in an amount to supply to said mixture at least about one-fourth part of alcohol per part of said sol and (b) a lubricating oil solution of a normal metal salt of an oil-soluble sulfonic acid having a molecular weight of from about 300 to about 800, the metal constituent of which is a metal of Group II of Mendelefls Periodic Table of the Elements, in an amount to supply to said mixture from about 0.1 to about 1.0 equivalent of metal per equivalent of Zinc supplied by said sol, whereby the colloidal zinc sulfide is extracted from said sol and redispersed in the lubricating oil, and (3) removing the water and alcohol from said mixture to isolate the colloidal dispersion of zinc sulfide in lubricating oil.

3. A method for preparing a colloidal dispersion of zinc sulfide in lubricating oil which comprises the steps of (l) forming an aqueous zinc sulfide sol, said sol containing from about 0.1% to about 5% of a protecting colloid, (2) forming a mixture of said sol with (a) methanol in an amount to supply to said mixture at least about onefourth part of methanol per part of said sol and (b) a lubricating oil solution of a normal zinc salt of an oil soluble sulfonic acid having a molecular weight of from about 300 to about 800, in an amount to supply to said mixture from 0.1 to about 1.0 equivalent of zinc per equivalent of zinc supplied by said sol, whereby the colloidal zinc sulfide is extracted from said sol and redispersed in the lubricating oil, and (3) removing the water and methanol from said mixture to isolate the colloidal dispersion of zinc sulfide in lubricating oil.

4. A method for preparing a colloidal dispersion of cadmium sulfide in lubricating oil which comprises the steps of (1) forming an aqueous cadmium sulfide sol, said sol containing from about 0.1% to about of a protecting colloid, (2) forming a mixture of said sol with (a) a Water-soluble aliphatic alcohol in an amount to supply to said mixture at least about one-fourth part of alcohol per part of said sol and (b) a lubricating oil solution of a normal metal salt of an oil-soluble sulfonic acid having a molecular weight of from about 300 to about 800, the metal constituent of which is a metal of Group II of Mendelefis Periodic Table of the Elements, in an amount to supply to said mixture from about 0.1 to about 1.0 equivalent of metal per equivalent of cadmium supplied by said sol, whereby the colloidal cadmium sulfide is extracted from said sol and redispersed in the lubricating oil, and (3) removing the water and alcohol from said mixture to isolate the colloidal dispersion of cadmium sulfide in lubricating oil.

5. A method for preparing a colloidal dispersion of cadmium sulfide in lubricating oil which comprises the steps of 1) forming an aqueous cadmium sulfide sol, said sol containing from about 0.1% to about 5% of a protecting colloid, (2) forming a mixture of said sol with (a) methanol in an amount to supply to said mixture at least about one-fourth part of methanol per part of said sol and (b) a lubricating oil solution of a normal cadmium salt of an oil-soluble sultonic acid having a molecular weight of from about 300 to about 800, in an amount to supply to said mixture from 0.1 to about 1.0 equivalent of metal per equivalent of cadmium supplied by said sol, whereby the colloidal cadmium sulfide is extracted from said sol and redispersed in the lubricating oil, and (3) removing the water and methanol from said mixture to isolate the colloidal dispersion of cadmium sulfide in lubricating oil.

6. A method for preparing a colloidal dispersion of molybdenum sulfide in lubricating oil which comprises the steps of (l) forming an aqueous molybdenum sulfide sol, said sol containing from about 0.1% to about 5% of a protecting colloid, (2) forming a mixture of said sol with (a) a water-soluble aliphatic alcohol in an amount to supply to said mixture at least about one-fourth part of alcohol per part of said sol and (b) a lubricating oil solution of a normal metal salt of an oil-soluble sulfonic acid having a molecular weight of from about 300 to about 800, the metal constituent of which is a metal of Group II of Mendelefis Periodic Table of the Elements, in an amount to supply to said mixture from about 0.1 to about 1.0 equivalent of metal per equivalent of molybdenum supplied by said sol, whereby the colloidal molybdenum sulfide is extracted from said sol and redispersed in the lubricating oil, and (3) removing the water and alcohol from said mixture to isolate the colloidal dispersion of molybdenum sulfide in lubricating oil.

7. A method for preparing a colloidal dispersion of molybdenum sulfide in lubricating oil which comprises the steps of (1) forming an aqueous sol of a molybdenum sulfide, said sol containing from about 0.1% to about 5,T-, of a protecting colloid, (2) forming a mixture of said sol with (11) methanol in an amount to supply to said mixture at least about one-fourth part of methanol per part of said sol and (b) a lubricating oil solution of a normal calcium salt of an oil-soluble sulfonic acid having a molecular Weight of from about 300 to about 800, in an amount to supply to said mixture from about 0.1 to about 1.0 equivalent of calcium per equivalent of molybdenum supplied by said sol, whereby the colloidal molybdenum sulfide is extracted from said sol and redispersed in the lubricating oil, and (3) removing the water and methanol from said mixture to isolate the colloidal dispersion of the molybdenum sulfide in lubricating oil.

References Cited in the file of this patent UNITED STATES PATENTS 1,922,006 Von Hoessle Aug. 8, 1933 1,955,211 Von Hoessle Apr. 17, 1934 1,969,166 Von Hoessle Aug. 7, 1934 2,126,925 Ryan et al Aug. 16, 1938 2,671,785 Vinograd et a1 Mar. 9, 1954 2,686,156 Arntzen et a1 Aug. 10, 1954 2,937,991 Carlyle May 24, 1960 3,013,968 Blake Dec. 19, 1961 

1. A METHOD FOR PREPARING A COLLOIDAL DISPERSION OF METAL SUFLIDE IN LUBRICATING OIL WHICH COMPRISES THE STEPS OF (1) FORMING AN AQUEOUS METAL SULFIDE SOL, SAID SOL CONTAINING FROM ABOUT 0.1% TO ABOUT 5% OF A PROTECTING COLLOID, (2) FORMING A MIXTURE OF SID SOL WITH (A) A WATER-SOLUBLE ALIPHATIC ALCOHOL IN AN AMOUNT TO SUPPLY TO SAID MIXTURE AT LEAST ABOUT ONE-FOURTH PART OF ALCOHOL PER PART OF SAID SOL AND (B) A LUBRICATING OIL SOLUTION OF A NORMAL METAL SALT OF AN OIL-SOLUBLE SULFONIC ACID HAVING A MOLECULAR WEIGHT OF FROM ABOUT 300 TO ABOUT 800, THE METAL CONSTITUENT OF WHICH IS A METAL OF GROUP II OF MENDELEEFF''S PERIODIC TABLE OF THE ELEMENTS, IN AN AMOUNT TO SUPPLY TO SAID MIXTURE FROM ABOUT 0.1 TO ABOUT 1.0 EQUIVALENT OF METAL PER EQUIVALENT OF METAL SUPPLIED BY SAID SOL, WHEREBY THE COLLOIDAL METAL SULFIDE IS EXTRACTED FROM SAID SOL AND REDISPERSED IN THE LUBRICATING OIL, AND (3) REMOVING THE WATER AND ALCOHOL FROM SAID MIXTURE TO ISOLATE THE COLLOIDAL DISPERSION OF METAL SULFIDE IN LUBRICATING OIL. 